High-frequency electrical system



Dec. 11, 1928. A 1,694,895

A. H. TAYLOR ET AL l 'HIGH FREQUENCY ELECTRICAL SYSTEM Filed May l5, 1924 l l l mme.; f Desired 7 Fmqaency IMI l l l L M75/VIVA #50E/VEP gvvvanlfoza Patented Dec. 11,*1928'. g f q A UNITED STATES PATENT' OFFICE.

ALBERT HOYT TAYLOR AND LEO C. YOUNG, F WASHINGTON, DISTRICT OF COIIZIU'IMBIA.-

HIGH-FREQUENCY ELECTRICAL SYSTEM.

Application led May 15, 1924. Serial No. 713,546.

quency electrical currents. The small capacity con-denser C, may be replacedby a high resistance. Binding post B4 connects to branch point P.

From a branch point P between the switch S and the condenser C1 a conn-ection leads to a condenser C2 having very small capacity,v and therefore high reactance to the flow of high frequency electrical currents. There is a connection from the condenser C2 to a binding post B2.

The second terminal of the coil L1 is connected to a binding post B3. Itis desirable that the connection of the coil L1 to the branch point P and the bin-ding post B3 be made of heavy wire or other form of low resistance conductor in order that the resistance of the path from the branch point P to the binding post B3 be a minimum.

j The unit is shown as housed in a screened container, which may be accomplished by lining a Wooden box with thin sheet metal or wire mesh, this screening being for the purlpose of preventing the magnetic fields of coils L1 and L2 from extending outside of the containerto establish magnetic couplings of these elements with nearby coils such as would be found in a receiver to which the unit is proposed to be connected. An antenna is shown connected to the binding post B1, a ground connection to the binding post 2, and a receiver to the binding post B2 and B3, and thus connected'. the peration is as follows:

T he high. frequency electrical currents collected in the antenna A are delivered to the branch point P through the low conductance element C1'. With the switch S closed, the currents arriving at the point P have the choice of going to ground E through two paths, one including the high reactance element C2 and the receiver, and the other including the'coupled rejector. The path including the coupled rejector isnormally of low impedance compared to the path includyWhile our invention relates generally to high frequency electrical systems, itv refers particularly to the reception of high frequency electrical currents or oscillat1ons such 5 as the reception of radio signals.

2 A particular object of our invention is the provision of a simple unit for connection to Aan antenna o'r collector of high frequency electrical oscillations and to a receiver of 1-0 such oscillations, the unit being for thepurpose of making the system more selectlve, permitting employment of a plurality of receivers connected to the same antenna without mutual adjustment interference, and for preventing a receiver which is capable of generating high frequency oscillations from efliciently transferring suchoscillations to the antenna and preventing the antenna from v eiiiciently radiating these oscillations. In a co-pending application we have fully described a high frequency electrical system having its various elements properly coordinated to obtain the objects of our invention, and in this application we describe and illustrate a conveniently arranged unit for employment in the high frequency electrical system whereby all of the advantages ascribed to our invention may be obtained.

Figure kl is a schematic diagram showing the application of my invention. "Fligure 2 illustrates the -employment of a part""of my invention as a wave trap. I

Referring to Figure 1 of the drawing L2 is 2 an inductance coil having in parallel therewith a variable condenser C2, the inductance `of the coil L2 and the capacity range of the condenser C., being properly selected to permit the circuit to be tuned oradj usted through a desired range of frequencies. The coil L1 40 'is preferably made of large wire or otherl form of conductor to offer very low resistance to high frequency electrical currents, and has a comparatively small' number of turns to .offer low reactancc to passage of high frequency electrical currents. i This arrangey ment provides a path of low impedance. The

coil L1 is preferably tightly coupled to the coil L2, as by being wound on the same form directly over the turns -of the winding of coil 50 L2. -Such an arrangement is known as a coupled rejector. Y

The switch S is in series with the coil L1, andthere is inserted between the switch S and a bindin vpostor electrical connector B,1 a condenser a low conductance tothe How of high fre- I of very small capacity to offer ing the high reactance element C2, and normally the currents will choose the coupled'rejector path and not affect the receiver. However,if the coupled rejector be tuned'to a frequency which it is desired to-select and send through the receiverwfor reception, the coupled rejector path will oder a high imypeda'nce to this frequency and force it to take the path through` the high reactance element C2, and if the receiver be tuned to this desired frequency .this tuning will aid in drawing the desired frequency current thr'oughithe high reactance element. With the coils L14 and L2 screened from the coils in the receiver Athere will be little or no magnetic coupling between these elements, which` coupling otherwise 'would 4tend to reduce the effectiveness of the high ieactance element C2.

As explained in our co-pending application Serial Number 713,545 filed May 15, 1924, a number of these units may be connected to a single antenna or collector A and `the low conductance element C1 and the high reactance element C, willpreventythe adjustment. of receivers and rejectors from interfering one with the other, thus enabling multiple reception of signals employing the same collector.

The capacity of the condenser C2 should ance is substituted for the condenser, depends upon not` only the frequency with which thel system is dealing but upon the extent of the collector or antenna A. If the antenna is short, such as 20 to '30 feet, it may be desirable to short circuit this ca acity C1. If the antenna is long, as from eet up, capacity or resistance is desirable. For an an- .tenna of about 90 feet in length we have found a capacity of from 25 to 100 micromicro-farads quite satisfactory. To operate successfully as a multiple system a small capacityat C1, or a high resistance, is practically essential in order to oavoid reactions between the several receivers and rejectors l when being adjusted. r

If the antenna is small and no capacity in series therewith is desired the unit as shown satisfactorily permits cutting out this element. This is accomplished 'by short circuiting the condenser C1, or by connecting antenna to binding post B4.

Figure 2 illustrates the employment ofthe unit of Figure 1 as a wave trap.vv By connecting the antenna A to the binding post B4, and the wire W.1 of the receiver to the Y binding post B3, there is provided a path from the antenna through the coupled rejector and receiver, all in series. The coupled rejectorwill permit all fre uencies to freely flow to the receiver, except t e one fre-E quency to which the coupled rejector is tuned, this arrangement being known as a wave trap instead of a rejector, one frequency being trapped out while all other frequencies are freely passed and not rejected.

Having described our invention we claim:

1. A high frequency electrical current se.

ing remote from said first mentioned termi-` nal connectors, connections between said additional pair of terminal connectors and vsaid high frequency signal receiving circuit,

a pair of fixed condensers interposed in said casing and electrically connected iny series with opposite ends thereof connected to one of said first mentioned terminal connectors and with one of said last mentioned pair of terminal connectors, connections intermediate said condensers with individual ones of said first mentioned pairs of terminal connectors, acoupled rejector within said casing and connected with an individual one of said first mentioned pairs of terminal connectors. and with an individual one of said additional pair of terminal connectors, a switch for bridging one pair of said first mentioned pairs of terminalconnectors, connections between another ofsaid first mentioned terminal connectors and one of Said additional terminal connectors with said radio frequency energy collecting system, whereby said coupled rej'ector may be selectively connected in shunt with said receiving circuit.

2. A high frequency electrical current selective unit for connection between the input of a` high fre iiency signal receiving circuit and a radio requency energy distribution circuit comprising a casing, an apparatus unit having terminals interposed in said radio frequency energy distribution circuit and in said signal receiving circuit, said apparatus unit including a pair of fixed condenser units interposed in series and connected between individual terminals on said casing, a coupled rejector within said casing connected with terminals thereon, and switching means carried by said casing for connecting saidcoupled re]ector with a point intermediate saidfixed condensers for preventing transfer of high frequency signaling energy from said high frequency signal receiving circuit to said high frequency energy distribution circuit..

ALBERT HoY'r TAYLOR. Lao o.YoUNG. i 

